You're dern skippy! On my honeymoon, my DH and I stood everywhere we rode the busses to in order that older folks, women with children, little ones, pregnant ladies and folks with injuries could sit in safety. When I went down and was obviously pregnant, people would push past me to get into a seat before I could. There were a few really great people who would see me clinging to my DH and insist that I take their seat (which I would loudly and gratefully thank them for) and some of these folks were people who rightfully should have remained seated.
The most shocking incident I have with this is when a very nice man offered me his seat next to his wife, and before I could lower myself into the seat, some half-drunken guy slides in directly beneath my lowering fanny! I debated letting my DH and the other husband pummel him, but decided to go ahead and finish lowering my large pregnant caboose right onto this guy's lap. I told him, and everyone on the bus that I had no problem sharing the seat with him, but that I hoped he was ok with the idea that I was 5.5 months pregnant and was still vomiting quite a bit. I also told him (loudly) that I hoped that I didn't cut the circulation off to the rest of his legs. He laughed and joked about it, saying that he couldn't tell that I was pregnant, and offered to let my husband be my seat-cushion for the ride, but I bet you a million dollars he'll be more careful about whose seat he steals next time.